1. Field of the Invention
The present invention relates to the testing of integrated optical circuits.
More specifically, the present invention relates to a method of characterization and non-destructive testing of an optical coupler associated with an integrated optical or optoelectronic circuit.
2. Discussion of the Related Art
Currently, integrated optical circuits are being more and more used in the field of telecommunications, especially for the transmission, the processing, or the storage of data. Integrated optical circuits may have many functions, such as multiplexing, demultiplexing, modulation, demodulation, spectral routing, amplification, storage, filtering, resonator . . . .
Integrated optical circuits are generally formed on and inside of wafers similar to those used in microelectronics. An integrated optical circuit comprises one or several elementary optical components processing one or several light beams. An integrated optical circuit is associated with optical couplers of introduction and/or extraction of a light beam into optical input and/or output waveguides.
The introduction and/or extraction of light is often performed through the edge of the chip on which the integrated optical circuits are formed. To test such circuits, it is thus necessary to separate each chip formed on a wafer. The test is then carried out on each individual chip by introducing a light beam through the chip edge.
Other types of couplers have been provided, such couplers being arranged at the surface of a wafer and being intended to receive and/or send light under a high incidence (greater than 45°) with respect to the wafer plane. For example, such couplers, which will be called surface-illuminated couplers herein, may be formed of a diffraction grating comprising an alternation of strips having different reflection coefficients or a succession of trenches formed in the wafer. In practice, the testing of circuits comprising surface-illuminated couplers is also carried out on diced chips, as is done for edge-illuminated chips.
As in the case of wafers comprising integrated electronic circuits, it is desired to test integrated optical circuits directly on the wafer on which they are formed, before dicing.
More specifically, there is a need for a method for testing a surface-illuminated optical coupler only involving measurements performed on a single surface of the wafer.